1. Field of the Invention
The present invention relates to a fluid pump such as a mechanically driven supercharger in an internal combustion engine.
2. Description of the Related Art
Known in the related art, e.g., Japanese Unexamined Utility Model Publication No. 62-61940, is a fluid pump having a rotary drive and a pair of rotors which are synchronously rotated by the rotary drive. This fluid pump comprises, as shown in FIG. 6, a drive shaft 40 which forms a part of the rotary drive and is driven by a drive source (not shown) such as a motor or a crankshaft of an engine, a pair of rotor shafts 41 and 42 supporting rotors 43 and 44, and identical mating gears 45 and 46 fixed on each end of the rotor shafts 41 and 42 and in mesh with each other. The rotor shaft 41 is rotated by the drive shaft 40 through the meshing of a gear 47 fixed thereto and another gear 48 fixed to the rotor shaft 41. In the above construction, since the drive-driven relationship between the rotor shafts 41 and 42 is unchangeable, then as shown in FIG. 7, only one tooth surface 49a of each tooth 49 of the gear 45 fixed on the rotor shaft 41 comes into contact with one tooth surface 50a of each tooth 50 of the gear 46 fixed on the rotor shaft 42. Additionally, loads in the direction of arrows F are imparted to bearings 51 and 52 supporting the rotor shafts 41 and 42 respectively, and therefore, both the gears 45 and 46, and the bearings 51 and 52 are worn nonuniformly, and thus the fluid pump has a poor durability.